Many novelists will tell you their characters are real. At least, inside their heads. Even Charles Dickens, according to Claire Tomalin's fabulous biography, used to find that some of his creations kept him company, metaphorically speaking, until the end of his life - and he hated having to kill them when his narratives demanded it.

Some writers populate their novels with actual people. I remember attending a talk by a very distinguished author who mentioned that she likes to know exactly how her protagonists look - and that having been unable to visualise one particular individual, she based his appearance on the politician Robin Cook.

My own characters, in past novels, were entirely fictional - but I've had a few distinctly spooky experiences. After I wrote Hungarian Dances (which was published in 2008) I kept on meeting my characters in real life - after the event. I'd consulted a Hungarian historian in Britain to check through the episodes set in the 1920s-50s, only to discover, when we finally got together for coffee, that her situation mirrored details of my heroine's life to a fairly crazy degree. After that, again and again I found life imitating art until, when people asked if the novel was based on reality, I could only say: "Yes, but I didn't know that when I wrote it..."

GHOST VARIATIONS is different, obviously, because 90 per cent of the protagonists are very real people. I can go on to Youtube and hear their recordings any time. Here, please enjoy Jelly d'Arányi's irresistible playing of a little piece by her compatriot Jenö Hubay. (And let's get the pronunciation straight right away. Yelly, please, not Gelly.)

These musicians were among the most celebrated of their day. Jelly was an enormously significant figure because so many composers wrote new music for her to play - including Ravel, Vaughan Williams, Bartók, Holst and Ethel Smyth. Myra Hess, her duo partner for 20 years, used to be a household name: the series of concerts she spearheaded at the National Gallery during the Blitz has gone into the realm of legend. I grew up listening to her recordings. Adila Fachiri, Jelly's sister, was likewise a celebrated violinist: she was one of the last pupils of their great-uncle, Joseph Joachim, and her playing is strong, rigorous, intellectual compared to Jelly's instinctive, playful, sensual sound. Donald Francis Tovey, Reid Professor of Music at Edinburgh University, was similarly distinguished: pianists today still use his editions of Bach's Well-Tempered Clavier, and his writings on music are unsurpassed in terms of insight, sensitivity and good sense. 

My experience of living with this cast of "fictional" characters has often felt, somewhat frustratingly, like watching them through the wrong end of the binoculars - tiny, distant figures who could be glimpsed, but not spoken to. I couldn't walk through Richmond Park imagining long conversations with them, or wonder if they'd be asking for second helpings at dinner, or any of the usual writery baggage. 

At least, not until the other day, when Jelly unexpectedly materialised to me, for the first time ever. At Bond Street Station.

There she was, beside me on the escalator, with her 1930s-style bobbed hair and sleek suit, pale skin, dark eyes, ready smile: a quiet but twinkly presence, tucking her arm through mine. She's taller than me (not that that's saying much) and seriously charismatic. Other people - if they could see her - would turn to look as she goes by. I was on my way to the Wigmore Hall, a venue at which she performed many times, along with Adila, Tovey, Bartók, Ravel and co. I've been going to concerts there for nearly 40 years, yet I've never been quite as conscious of the place's heritage, the ghosts that populate its richesse of space and sound. The concert was a superb piano trio (Raphael Wallfisch and friends) in a programme of big, heady, extrovert pieces from Beethoven to Rachmaninov. The seat beside mine was empty - except that Jelly sat there, watching the musicians' every move, smiling constantly and sometimes singing along. What? My heroine, real-life and all, sings along in other people's concerts? Then yesterday we went out for lunch - me and, unexpectedly, Jelly - and before heading home I popped down to the ladies' room. Back at the top of the stairs I realised that my invisible companion had not yet rejoined me - because she was still in the cloakroom, powdering her nose very, very thoroughly. 

I think Jelly, in her fictional form, has possibly become "real" all of a sudden because this book has, too, since we launched the campaign for it four days ago. 

That means you've helped to make it happen. Thank you - and I hope you will love our heroine, the one and only Jelly, as much as I do.